The present invention relates to a rolling bearing and, more particularly, a rolling bearing in which a current can be passed between the inner ring and the outer ring, that are rotated relatively.
Normally, in case the motor is driven by the sinusoidal wave of the commercial power supply, the electrolytic corrosion of the rolling bearing due to the charges that are generated in the rotating shaft of the rotor is not caused. Thus, it is the existing circumstances that no countermeasure for the electrolytic corrosion of the bearing is taken.
However, in the case that the motor is driven by using the inverter unit, the rotor is brought into the state that it is floated electrically over the stator, and thus the charges are generated in the rotating shaft by the harmonics and the electrostatic capacity. Then, the accumulated charges can be discharged only via the rolling bearing as the support point of the rotating shaft. Thus, the charges are discharged from inner ring of the rolling bearing to the outer ring via the rolling elements to electrolytically corrode the race surfaces.
For this reason, there is proposed the rolling bearing that can prevent the electrolytic corrosion by connecting the rotating shaft and the structural body such as the bracket, etc., that holds the rolling bearing, via the rolling bearing, that is made electrically conductive, such that the charges accumulated in the rotating shaft of the rotor are caused to escape to the structural body such as the bracket.
FIG. 5 is a sectional view of the rolling bearing in the prior art, that is set forth in the Unexamined Japanese Patent Application Publication No. Hei1-307516. In FIG. 5, in the rolling bearing 30, the balls (rolling elements) 33 arranged between the inner ring 31 and the outer ring 32 are held by the holders 34, 34, and the sealing member 35 is spread between the inner ring and the outer ring in the situation that the lubricating grease containing the carbon black to have the conductivity is filled between the inner ring 31 and the outer ring 32. Also, the raceway surface 31a of the inner ring 31 has a radius larger than the balls 33, and the clearance 36 between the balls 33 and the raceway surface 31a of the inner ring 31 acts as the grease guiding means.
The lubricating grease containing the carbon black to have the conductivity is filled between a pair of races that guide the balls 33 held by the holders 34, and such lubricating grease is sealed by the sealing member 35, and the grease containing the carbon black is guided to the raceway surfaces of the races as it is by the grease guiding means 36, so that the contact to the balls 33 with the conductivity can be accomplished.
In the above rolling bearing, there is the problem that, since the lubricating grease containing the carbon black to have the conductivity is employed, such grease is inferior in lubricity and life to the normal lubricating grease.
FIG. 6 is a sectional view of the rolling bearing in the prior art, that is set forth in the Unexamined Japanese Patent Application Publication No. Hei9-291943. In FIG. 6, 40 is the rolling bearing, 41 is the metal inner ring for rotatably supporting the rotating shaft (not shown), 42 is the rolling element such as the steel ball, etc., 43 is the metal outer ring held to the structural body such as the bracket (not shown), etc., 44 is the sealing member formed of the conductive flexible member that comes in contact with the inner ring 41 and the outer ring 43 to cover the rolling elements 42 from both ends away therefrom, and 45 is the lubricating grease for lubricating the rolling surfaces of the inner ring 41 and the outer ring 43.
Since the inner ring 41 and the outer ring 43 are brought into contact with each other via the sealing member 44 formed of the conductive flexible member, the charges generated in the rotating shaft (not shown) are caused to escape from the inner ring 41 to the structural body such as the bracket (not shown), etc. via the sealing member 44 and the outer ring 43.
In the above rolling bearing, since the sealing member 44 formed of the conductive flexible member is brought into contact with the inner ring 41 and the outer ring 43 by the spring force of the flexible member, there is the problem in aspects of wear and dustproof property.
The present invention is made to overcome above problems, and it is an object of the present invention is to get a rolling bearing having lubricity and life that are equivalent to those of the normal rolling bearing using the lubricating grease and having conductivity between an inner ring and an outer ring.
A rolling bearing of the present invention which has a metal inner ring for rotatably supporting a rotating shaft, a metal outer ring held in a structural body such as a bracket, and rolling elements arranged between the inner ring and the outer ring and in which a grease for lubricating rolling surfaces of the inner ring and the outer ring is sealed, the rolling bearing has a current passing sealing structure which comprises a first current passing plate fitted to an end portion of the inner ring, and a second current passing plate fitted to an end portion of the outer ring, and in which a conductive grease is sealed between the first current passing plate and the second current passing plate.
Also, the current passing sealing structure is constructed such that the second current passing plate is formed to have a U-shaped sectional shape whose opening portion is directed to an inner ring side, the first current passing plate is arranged on an inside of the U-shaped sectional shape, and the conductive grease is sealed in the inside of the U-shaped sectional shape.
Also, the current passing sealing structure is constructed such that the second current passing plate includes two current passing plates arranged on both sides of the first current passing plate, and the conductive grease is sealed in a space formed between two current passing plates.
Also, a rolling bearing which has a metal inner ring for rotatably supporting a rotating shaft, a metal outer ring held in a structural body such as a bracket, rolling elements arranged between the inner ring and the outer ring, a grease for lubricating rolling surfaces of the inner ring and the outer ring is sealed, and a sealing plate for sealing the grease, the rolling bearing has a current passing sealing structure which comprises a first current passing plate fitted to be put between an end portion of the inner ring and a contact surface of stepped portions of the rotating shaft, a second current passing plate fitted to the sealing plate to surround the first current passing plate by putting between the outer ring and an inside of the bracket, and a conductive grease sealed into a space between the second current passing plate and the sealing plate.